1. Field of the Invention
This invention relates generally to parachute packs and more particularly to parachute packs having a compression spring-loaded pilot chute which is deployed to release and deploy a main parachute canopy from its container.
2. Background and Prior Art
Parachute packs with pilot chutes are typically used as reserve parachutes worn on the chest of the chutist as a safety precaution in the event that the main chute worn on the back fails to deploy or deploys improperly.
Parachute packs are known in the art. See, e.g., U.S. Pat. Nos. 3,262,660, 3,908,937 and 4,898,346.
Because of the backup purpose of the reserve chute, the force required to release the retainer mechanism is limited by Federal law to a maximum of 22 lbs. as a safety precaution. This force is determined by the amount of tension exerted on the compression spring by the retainer mechanism.
According to the prior art parachute pack disclosed in U.S. Pat. No. 3,908,937, the pilot chute is deployed by a compression spring which is held in a tensioned state against the pack by a pair of retaining cords which pass from opposing sides of the pilot chute and are retained against the main chute container by a pair of retaining pins which are mutually connected to a single ripcord.
The two retainer pin configuration presents an inconvenience in packing of the parachute pack as two separate retainer cords must be threaded through the pack and secured at the opposite surface thereof with two separate retainer pins, requiring the use of special tools. Additionally, because of the two-point loading of the spring, there is a possibility that the compression spring will tilt upon deployment, causing the pilot chute to be improperly projected from the pack.
Another disadvantage in the prior art is that pack thickness varies according to the size of the main canopy or the particular placement and packing technique used. Since the retainer cords are of a predetermined fixed length, the tension will vary according to the particular packing technique or canopy size utilized.
Yet another disadvantage in the prior art is the possibility that the main canopy may "float" or lift away from the wearer before the requisite positive drag force is attained by the pilot chute. This is caused by the fact that the deployment of the pilot chute will cause the flaps to open to a flat configuration allowing an air stream to pass under the main canopy. If the air stream carries the main canopy out of the container before the pilot chute attains sufficient positive drag, an out of sequence deployment will result.
An attempt has been made to improve upon the conventional parachute pack in which a single retainer cord is disposed in the center of the pack and extends through the center of the compression spring. Such is disclosed in U.S. Pat. No. 4,898,346. A convex disc is attached to the top of the pilot chute, and the retainer cord passes through an aperture in the center of the disc and is diverted to one side of the disc where it is anchored into a second aperture or grommet in the disc.
Since the retainer cord is presized to be of a fixed length before packing of the parachute pack, adjustment of the tension on the retaining cord after assembly is not possible. Because of the single cord design, the pilot chute and disc assembly may be inadvertently rotated while being worn. In such case, the retainer cord will twist up, increasing the tension on the compression spring and consequently increasing the amount of force needed to pull the retainer pin to release the pilot chute. Additionally, the method of attachment of the cord to the pilot chute disc may asymmetrically load the disc, causing the compression spring to be at an improper angle and resulting in improper deployment of the pilot chute.
In addition, the main parachute is subject to undesirable "floating" prior to attainment of sufficient positive drag by the pilot chute.